Although fibre-reinforced-concrete (FRC) is increasingly used, it has been occasionally applied to water-retaining structures (WRSs), and no comprehensive design guidelines are currently available for the design of WRSs with FRC. A design methodology for such applications based on available recommendations and research has been applied to three reference scenarios representing a wide range of WRSs: a flood defence wall, a weir wall, and a swimming pool wall. For each of these scenarios, alternative designs using different FRC mix designs have been compared through the statistical analysis of several relevant parameters. This study confirms that the use of FRC significantly reduces reinforcement requirements when compared to conventional reinforced concrete solutions. Clear trends have been identified between the structural performance of the resulting WRS designs, the FRC mix characteristics and the fibre type and dimensions. This study has considered not only structural performance but also the total cost and environmental footprint per unit length of WRSs, and these considerations further the case for adoption of FRC in such applications. Overall, fibre dosages below 0.75% and 2% in volume for steel and synthetic fibres, respectively, can lead to WRS designs with lower cost and carbon footprint than their reinforced concrete counterparts.